1. Field of the Invention
The present invention relates to an ink jet recording apparatus incorporating a recording head which discharges ink from a discharge opening so as to record desired information. More particularly, the present invention relates to an ink jet recording apparatus having a waste ink collecting section for collecting waste ink cleared by a recovery means which maintains and recovers excess ink from the recording head.
2. Description of the Related Art
Ink jet recording apparatus having a discharge recovery function for maintaining and recovering excess ink cleared from a recording head are known. During the recovering operation, ink is cleared from the discharge opening in the recording head without being used for recording. In most of the known apparatuses of the type described, the waste ink cleared from the discharge opening is collected in a waste ink collecting section through tubing or the like and is then discarded.
Hitherto, various types of waste ink collecting systems have been proposed. For instance, a system has been proposed in which the waste ink is discharged into a disposable tray which can be removed from the apparatus and discarded. Another known system employs a waste ink reservoir which is replaceably mounted in the apparatus and which is provided with an ink absorber. In still another known system, the waste ink is returned to a waste ink reservoir integrated with the ink cartridge which stores the fresh ink that is supplied to the recording head.
In the system which employs the waste ink reservoir, it is necessary to change the reservoir as stated above, since the volume of the waste ink in the reservoir increases whenever the ink is cleared. In a system of the type in which the waste ink reservoir is integrated with the ink cartridge, the ink cartridge and, hence, the waste ink reservoir are changed each time the fresh ink supply for recording is exhausted, regardless of the amount of waste ink present in the waste ink reservoir.
Other proposals include a waste ink collecting system having a waste ink reservoir with a volume large enough to contain the total amount of waste ink which is expected to be generated during a possible period of operation of the recording apparatus, and a waste ink collecting system having means for sensing the amount of waste ink in an waste ink reservoir which signals the user that it is necessary to change the waste ink reservoir, thus enabling the reservoir to be changed at suitable intervals.
These known waste ink collection systems, however, suffer from the following disadvantages.
Namely, in the system of the type in which the waste ink reservoir is replaced together with the ink cartridge regardless of the amount of the waste ink collected in the reservoir, problems arises because reservoir may hold either very little or too much waste ink when the fresh ink in the reservoir has been consumed. In the former case, the waste ink reservoir is replaced unnecessarily, whereas, in the latter case, the recorded image and/or the operator's hand may become dirty should the waste ink reservoir overflow or leak waste ink. In the worst case, the operation of the recording apparatus itself may be impeded because of the waste ink leaking from the reservoir.
The collection system having a waste ink reservoir large enough to contain the total quantity of waste ink expected to be generated throughout the entire life of the recording apparatus is also impractical because the size and the cost of the apparatus are increased due to extremely large size of the waste ink reservoir needed. In addition, since the total amount of the waste ink which can be stored is still limited, flooding of the waste ink and the ensuing contamination of the apparatus may still take place when there is excessive usage, for example, when there is an increase in the volume of the wasted ink due to the erroneous operation by the operator.
The aforementioned system which is able to sense the amount of waste ink collected in the waste ink reservoir has been proposed to obviate these problems. In one version of this system, means is provided for preventing operation of the recording apparatus unless the waste ink reservoir is changed once the reservoir is filled up with the waste ink. This improved system is widely used because of its high reliability in regard to the handling of the waste ink.
Various other methods, such as methods for sensing the pressure or weight or optically sensing the level of collected waste ink have been proposed to enable sensing the volume of the waste ink stored in the waste ink reservoir. These methods, however, require complicated sensing devices which not only raise the cost of the recording apparatus but also reduces the volume of the waste ink that can actually be collected in the ink reservoir because they occupy a considerable volume of space, with the result that the frequency with which the waste ink reservoir must be changed is increased undesirably.